The primary aim of the study outlined in this protocol is to demonstrate drug-induced differences in limbic activation during an fMRI-based emotional face recognition task following acute administration of zolpidem, alprazolam, and the positive control caffeine in healthy volunteers. Although zolpidem may exhibit a similar behavioral pharmacological profile to the conventional BZs in many instances, its relative GABAA receptor selectivity distinguishes it from its non-selective counterparts. Thus it is hypothesized that the anxiolytic alprazolam (1 mg) will reduce the BOLD response to emotional faces within the amygdala and insula similar to other anxiolytics (e.g., lorazepam, diazepam, and pregabalin), while the hypnotic zolpidem (10 mg) will not cause such a reduction. It is hypothesized further that because adenosine receptors have been localized to the amygdala and caffeine has been shown to be anxiogenic, an acute challenge with a moderate dose of caffeine (200 mg) will enhance the BOLD response in the amygdala and/or insula during the face recognition task. The data that will be collected in this aim will provide the first in vivo brain imaging evidence for different actions based on the different GABAA receptor pharmacological profiles of zolpidem and alprazolam, and will support their clinical roles in the treatment of insomnia and anxiety, respectively.